The most serious risk involved in TMS therapy is the possibility of experiencing a grand mal seizure, but this is a rare side effect. Only 1 in 10,000 patients will experience a grand mal seizure during transcranial magnetic stimulation therapy.
Otherwise, the most common side effect is experiencing headaches after the first two or three treatments. This is because the brain is not used to experiencing targeted magnetic pulses, much less many pulses over consecutive days. It is also not used to feeling copper coils pressed against the scalp, causing the muscles to tense up and become achy for a few days. After the first week of treatment, however, the vast majority of patients stop experiencing headaches as the scalp becomes accommodated to the twin coils and pulses.
Our technicians have had three patients out of several hundred experience fatigue as a side effect of TMS therapy. One patient experienced mild sleepiness and the other two developed extreme but temporary fatigue for a day following the procedure.